In Talend Studio Repository tree view, click Job Designs > Joblets to expand the Joblets node.
The same way as for the Job Designs, you can create folders via the right-click menu to gather together families of Joblets. Right-click on the Joblets node, and choose Create folder. Give a name to this folder and click OK.
If you have already created Joblets that you want to move in this new folder, simply drag and drop them into the folder.